Optical detection device for a counter

ABSTRACT

An optical detection device for a counter, comprising a consumption indicator, formed from a rotating target ( 4 ) and optical elements of the emitter type and receiver type, at least one of which is opposite the target, the received optical signal from which is used to infer the number of rotations of the disc. The above comprises at least two optical elements ( 6 A,  6 B) of one type and at least one optical element ( 7 ) of the other type. The target ( 4 A) is an opaque disc section with a centre angle, called the first angle (γ), of 45 to 225°. The two optical elements of one type ( 6 A,  6 B) are emitter elements of a beam of light, the beam of light lies outside the target ( 4 ) and the device further comprises at least one mirror ( 4 A,  4 B), reflecting each optical beam onto the target trajectory.

The present invention pertains to an optical detector device for ameter, a fluid meter in particular e.g. water, to enable remote readoutof the consumption of this water meter, or equivalent operations oflogging or alert type.

More precisely it concerns an optical detector device for a meter,comprising a consumption indicator formed of a rotating target andoptical elements of emitting and receiving type of which at least onelies opposite said target, whose received optical signal is processed toinfer at least the number of rotations of said target, comprising atleast two said optical elements of one type and at least one saidoptical element of the other type.

Said device is known from patent EP 0 380 794.

According to this document, the device comprises an optical detectorwhich is arranged outside the meter and which is adapted to produce aneffective signal whenever an index or active sector arranged on a discpasses in front of the detector. This signal is amplified and convertedinto a square wave so that it can be sent onto a data transmissionnetwork. With said detection device, it is possible to determine thenumber of disc rotations but it is not possible to determine thedirection of rotation of this disc.

Yet a fluid meter, in particular a water meter, can operate both onfluid input and on fluid output. This is the case for example when watermains are emptied during construction works, or on flow surges causingwater return movement.

The consumption display device, for example an arrangement of dials withdigits, takes this into consideration.

The purpose of the invention is to provide an optical detector deviceable to determine the direction of flow of the water and hence thedirection of rotation of the indicating disc so as to take into accountconsumption which can be termed negative and to provide identicalconsumption data to the data provided by the conventional display deviceof the meter.

For this purpose, the invention proposes an optical detector device fora meter comprising a consumption indicator formed of a rotating targetand optical elements of emitting type and receiving type of at least onelies opposite said target, and whose received optical signal isprocessed to infer at least the number of rotations of said target,comprising at least two said optical elements of one type and at leastone said optical element of the other type, characterized in that saidtarget is a portion of an opaque disc with a centre angle called firstangle lying between 45 and 225°, and said second optical elements of onetype are elements emitting a light beam whose light beam is outside thetarget, and in that it also comprises two mirrors reflecting eachoptical beam on the pathway of the target.

These optical elements may be integrated in one same component and anappropriate cover on the meter and module may limit stray light beams.

The disc portion preferably has a centre angle of 180°.

The choice of an opaque disc having a centre angle of 180° ensuresoptimisation of the frequency of the transmitter element or elements inrelation to electric power consumption. Said meters or said modules arebattery powered and it is highly advantageous that they should have lowpower consumption. A single light beam sequence may be chosen which isoptimal irrespective of detected states. This single sequence ensuresequilibrium of states in terms of angle and duration at constant speed.

Preferably the optical detector of the invention comprises two emittingoptical elements and one receiving optical element.

This embodiment has the advantage of being the least costly, opticalemitters generally being less expensive than optical receivers.

According to another variant, the device comprises two emitting opticalelements and two receiving optical elements associated in pairs, eachreceiving element receiving the optical beam from the emitting elementin the same pair.

Advantageously, the two optical emitters operate sequentially.

Advantageously, the three optical elements are substantially aligned andthe receiving optical element lies between the emitting elements.

The positioning of the elements may be such that that the angle ofincidence of the optical beam emitted and received by the opticalelements is less than 60°.

The device may comprise at least one collimator device for the opticalbeam and this collimator device may comprise slits to limit strayinterference between light beams.

With this arrangement it is possible to obtain sharper state transitionsand improved coupling between the optical emitters and receivers.

According to a variant of embodiment, the device comprises an additionaloptical emitter who trace on the disc is centred on the axis of symmetryof the disc, the disc being provided with a reflecting zone about thisaxis.

The invention also concerns a fluid meter comprising a rotating discthat is part of an optical detector device such as specified above.

Finally the invention concerns a detection module intended to cooperatewith a fluid meter and comprising said optical elements that are part ofa device such as specified above.

Advantageously, this module also comprises a collimation device for theoptical beam.

The invention is described below in more detail with the aid of figureswhich only show one preferred embodiment of the invention.

FIG. 1 is a view of the meter and of a module according to theinvention.

FIG. 2 is a cross-section view of a detection device of the inventionaccording to a first embodiment.

FIG. 3 is an overhead view of a rotating target that is part of adetection device of the invention, in different positions.

FIG. 4 is a diagram illustrating processing of the data detected by thedetection device of the invention.

FIG. 5 is a partial cross-section view of a variant of embodiment of adetection device of the invention.

FIG. 6 is partial cross-section view of another variant of embodiment ofa detection device of the invention.

FIG. 7 is a cross-section view of a detection device of the inventionaccording to a third embodiment.

FIG. 1 is a front view of a fluid meter 1, more precisely a water meter,comprising a casing 2 provided with a water inlet pipe and outlet pipesurmounted by a totallizer 3 containing a transmission and shaftrotation gear mechanism for a measuring element such as a turbine orvolumetric chamber contained in casing 2 which transmits to aconsumption display device not shown, and a rotating indicator target 4parallel to an upper transparent wall of the totallizer.

An optical detection module 5 whose lower wall is at least partlytransparent, is positioned on the upper wall of meter 1 in order todetect water consumption and its direction of flow.

FIG. 2 illustrates the optical detection device of the invention in moredetail.

Meter 1 therefore comprises a transparent wall 1A and parallel to thiswall is an indicator target 4 driven by a transmission mechanism. Thistarget is a portion of an opaque disc with a centre angle of between 45and 225° and is preferably 180°.

Arranged so that they arrive opposite the target 4 or in the vicinitythereof when the module is positioned on the meter 1, module 5 comprisesthree optical elements, more precisely two optical emitters 6A,6B eacharranged on either side of an optical receiver 7. When considering axisA of disc 4, the optical receiver 7 is offset from this axis A and thethree optical elements 6 a, 6B and 7 are aligned parallel to a radius ofdisc portion 4.

The two emitters 6A, 6B emit a light beam outside target 4 and thedetection device also comprises two mirrors 4A, 4B reflecting eachoptical beam on the pathway of target 4.

Instead of two separate mirrors 4A, 4B as shown, only one mirror may beused ensuring the reflection of the two optical beams emitted byemitters 6A and 6B.

Preferably, the optical emitters 6A, 6B are LED diodes emitting aninfrared beam which passes through the two transparent walls 5A, 1A andis reflected on a mirror 4A, 4B.

If this reflected beam is not intercepted by the target 4 (as on theright in FIG. 2), it is received by the optical receiver 7 preferablyformed of a photodiode or phototransistor. If it is intercepted by thetarget 4 (as on the left in FIG. 2), it is not received by the receiver7.

FIG. 3 shows different relative positions of the target 4 and ofemitters 6A, 6B and receiver 7 as seen along a plane perpendicular toaxis A of the disc.

The direction of rotation of the disc is shown by an arrow, thisdirection corresponding to normal positive fluid consumption.

In position 3A, the two beams of emitters 6A, 6B and their reflectedbeams are located outside target 4. The optical signals sequentiallyreceived by receiver 7 are maximum and are derived from the two emittedbeams. A pair of values of (1,1) is therefore detected.

In position 3B, the beam from emitter 6A and its beam reflected bymirror 4A are located outside the target 4. The beam from emitter 6B hasits beam reflected by mirror 4B which on the other hand is interceptedby target 4. Receiver 7 therefore only receives the first reflected beamand the pair of values detected is (1,0).

In position 3C, the two beams from emitters 6A, 6B have their reflectedbeams intercepted by the target 4. The optical signal received byreceiver 7 is substantially zero. A pair of values of (0,0) is thereforedetected.

In position 3D, the beam from emitter 6A has its beam that is reflectedby mirror 4A intercepted by target 4. The beam from emitter 6B and itsbeam reflected by mirror 4B are outside the target 4 however. Receiver 7therefore only receives the second reflected beam and the detected pairof values is (0,1).

In positive consumption, the series of signals received is therefore(1,1), (1,0), (0,0), (0.1) and the frequency of their state changesmakes it possible to determine the speed of rotation of the indicatortarget 4 and hence consumption. A series comprising one of the precedingpairs in another order enables detection of a change in the direction ofrotation of indicator target 4 and hence a negative consumption.

Instead of operating as above, it is possible to seek to identify asmall so-called minimum transmission through disc 4, instead of seekingto identify total opacity and zero transmission.

Therefore with the invention it is also possible to detect thepositioning of the module on the meter. The signal may have threevalues:

-   -   zero, indicating that the module is not positioned,    -   minimum, indicating transmission through disc 4,    -   maximum, indicating transmission outside disc 4.

These signals schematised in square waves are shown in FIG. 4. Theprocessing of these signals does not require any complex electronics andthey can be processed directly by a microcontroller.

In the above, for the purpose of simplifying the description, often onelight pulse was concerned emitted by diodes 6A, 6B over a quarterrotation of disc 4. According to the invention, the optical emitters 6A,6B operate in sequence which makes it possible to determine signals andthe corresponding states and has the advantage of requiring low overallpower consumption. The light beam is emitted in the form of frequencypulses related to the maximum rotation speed of the target.

In the above, optical elements 6A, 6B, 7 are advantageously SMD opticalcomponents (Surface Mounted Devices) and are simple i.e. the componentshave no integrated collimation.

As can be seen in FIG. 5, optical beam collimation devices 8, of lenstype, may be inserted between the transparent wall 5A of module 5 andthe optical elements 6A, 6B, 7, or they may be formed directly by thetransparent wall 5A of module 5 configured as a collimation device.

Optical elements 6A, 6B, 7 here may also be SMD components (SurfaceMounted Devices).

FIGS. 6 and 7 illustrate variants of embodiment of the invention.

Although a sealing device may be provided between the reading module andthe totallizer, of gasket or press fit type for example, solid or liquiddirt or particles may be deposited on the transparent wall 1A of meter1, interfering with transmission of the light beam through thetransparent walls 1A, 5A of meter 1 and of detection module 5.

As can be seen in FIG. 7, to minimize this interference, opticalelements 6A, 6B, 7 are conformed so that the angle of incidence B isvery small and preferably less than 60°. Therefore any power losses ofthe beam due to particles or dirt are minimum and the beam transmittedthrough the transparent walls remains of high power.

One solution for minimising this angle of incidence B is to choose anadequate distance between the optical elements and the disc, angle Bbeing smaller the greater this distance.

FIG. 6 illustrates another possibility.

Here the optical receiver 7 is arranged with its axis of symmetryoriented in the direction of the light beam perpendicular to thetransparent wall 1A of the module, and the two optical emitters 6A, 6Bhave their own equivalent axis of symmetry in a plane perpendicular tothis wall 1A but at an angle C with respect to this axis of symmetry ofthe central optical receiver 7. Preferably, this angle C is less than60°. Also the receiver 7 is positioned above the emitting diodes 6A and6B to avoid any direct coupling between emitter and receiver withoutpassing through the rotating target.

In the above description, the optical detector device of the inventioncomprises two emitting optical elements and one receiving opticalelement which receives the two emitted optical beams. These arrangementsare particularly economical having regard to the cost of a photodiode orphototransistor.

However, while remaining within the scope of the invention, it ispossible to use two emitting optical elements and two receiving opticalelements, associated in pairs, each receiving element receiving theoptical beam of the emitting element in the same pair.

Said detection device of the invention is shown in FIG. 7.

Two pairs each comprising an optical emitter 6A′, 6B″ and an opticalreceiver 7′, 7″ are arranged in the module. Each emitter 6A′, 6B″ emitsan optical beam through the walls opposite module 5A and meter 1A, andthe effects are the same as previously described for FIG. 3.

As has already been seen, in order to minimize interference by solid orliquid dirt or particles in the transmission of the light beam throughthe transparent walls 1A, 5A of meter 1 and of the detection module 5,the angle of incidence B of the beams is small and preferably less than60°. For this purpose, the optical elements 6A′,7′, 6B″, 7″ arepreferably inclined at this angle B with respect to the plane ofsymmetry of each pair, perpendicular to the walls of module 5A or meter1A.

Following the same optical principle, it is possible to provide adetection device to detect the presence of the module on the meter. Anoptical emitter common to the detection device already described ordedicated to presence detection 10 is then arranged so that its emittedbeam is reflected on a reflecting surface S arranged on the disc 4 aboutthe axis of rotation A. The absence of a reflected beam indicates thatthe module is not positioned on the meter. Any change in this reflectedbeam indicates that the module is not properly positioned on the meter.

Advantageously, a dedicated additional optical emitter 10 is used forthis purpose, this emitter being centred for example on disc 4. Moregenerally, the trace of the optical beam emitted by this emitter on disc4 is centred on axis A shown in FIG. 3.

1. Optical detector device for a meter, comprising: a consumptionindicator formed of a rotating target and optical elements of emittingtype and receiving type of which at least one lies opposite said target,whose received optical signal is processed to infer at least the numberof rotations of said disc, having at least two said optical elements ofone type and at least one said optical element of the other type,wherein said target is a portion of an opaque disc with a center anglecalled a first angle (γ) of between about 45 and about 225°, and saidtwo optical elements of one type are emitting elements of a light beam,whose light beam is outside target and in that it also comprises atleast one mirror reflecting each optical beam on the pathway of thetarget.
 2. Device as in claim 1, wherein said disc portion has a centerangle (γ) of 180°.
 3. Device as in claim 1, further comprising twoemitting optical elements and one receiving optical element.
 4. Deviceas in claim 3, wherein said three optical members are substantiallyaligned and the receiving optical element is between the emittingelements.
 5. Device as in claim 1, further comprising two emittingoptical elements and two receiving optical elements associated in pairs,each receiving element receiving the optical beam of the emittingelement in the same pair.
 6. Device as in claim 1, wherein the twooptical emitters operate in sequentially.
 7. Device as in claim 1,wherein the positioning of said optical elements is such that the angleof incidence (B) of the optical beam emitted and received by the opticalelements is less than 60°.
 8. Device as in claim 1, further comprisingat least one collimator device for the optical beam.
 9. Device as inclaim 8, wherein said collimator device has slits limiting strayinterference between light beams.
 10. Device as in claim 1, furthercomprising an additional optical emitter whose trace on the disc iscentred on the axis of symmetry (A) of the disc, the disc being providedwith a reflecting zone about this axis (A).
 11. Fluid meter comprising:a rotating disc that is part of an optical detector device as inclaim
 1. 12. A detection module intended to cooperate with a fluid meterand comprising said optical elements that are part of a device as inclaim
 1. 13. A module as in claim 12, further comprising an optical beamcollimator device.